The present invention relates to a control apparatus for an automatic transmission gear system for vehicle, having a function for reducing change in output torque change during gearshift.
As disclosed in Japanese Patent Publication No. 54-35631, page 7, column 13, lines 5 to 25, automatic transmission gear system for vehicle is controlled such that, e.g., during "power on" downshift from the third speed to the second speed, an engaging force of a disengaging-side engaging element (clutch 17) and that of an engaging-side engaging element (brake 18) are properly overlapped with each other so as to reduce a downshift shock.
In an automatic transmission gear system for vehicle having the above arrangement, the engaging-side engaging element is started to be engaged substantially at the same time the disengaging-side engaging element is started to be disengaged, so that excessive running up of an engine during "power on" downshift (i.e., an engine coupled to an input shaft of a transmission tends to excessively rotate when the disengaging-side engaging element is started to be disengaged) is prevented and a drop in an output shaft torque is reduced because of simultaneous disengagement of the disengaging- and engaging-side engaging elements. However, since it is difficult to properly control a time interval of an overlapping period or a timing at which the engaging-side engaging element is started to be engaged, the above object cannot be sufficiently achieved.